Rivet analyses

title: BESIII_2013_I1203840

$\psi(2S)\to \bar{p}K^+\Sigma^0$ and $\chi_{cJ}\to\bar{p}K^+\Lambda^0$

Experiment: BESIII (BEPC)

Inspire ID: 1203840

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 87 (2013) 1, 012007

Beams: * *

Beam energies: ANY

Run details: - Any process producing psi(2S) and chi_c originally e+e-

Measurements of mass distributions in the decays $\psi(2S)\to \bar{p}K^+\Sigma^0$ and $\chi_{cJ}\to\bar{p}K^+\Lambda^0$. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2013_I1203840.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> pbar K+ Sigma^$ and chi_cJ -> pbar K+Lambda class BESIII_2013_I1203840 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1203840);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 20443 or Cuts::pid == 445 or Cuts::pid == 10441
                                            or Cuts::pid == 100443);
  declare(ufs, "UFS");
  DecayedParticles chi(ufs);
  chi.addStable(PID::PI0);
  chi.addStable(PID::K0S);
  chi.addStable(PID::SIGMA0);
  chi.addStable(PID::SIGMA0);
  chi.addStable(PID::LAMBDA);
  chi.addStable(-PID::LAMBDA);
  declare(chi, "chi");
  // histograms
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h_psi[ix], 1, 1, ix + 1);
    for (unsigned int iy = 0; iy < 3; ++iy) book(_h_chi[iy][ix], 2, iy + 1, ix + 1);
  }
  book(_h_pLam, 3, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{-2212, 1}, {3212, 1}, {321, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{2212, 1}, {-3212, 1}, {-321, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{-2212, 1}, {3122, 1}, {321, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{2212, 1}, {-3122, 1}, {-321, 1}};
  DecayedParticles chi = apply<DecayedParticles>(event, "chi");
  // loop over particles
  for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
    int sign = 1;
    if (chi.decaying()[ix].pid() == 100443) {
      if (chi.modeMatches(ix, 3, mode1)) {
        sign = 1;
      }
      else if (chi.modeMatches(ix, 3, mode1CC)) {
        sign = -1;
      }
      else
        continue;
      const Particle& pbar = chi.decayProducts()[ix].at(-sign * 2212)[0];
      const Particle& Kp = chi.decayProducts()[ix].at(sign * 321)[0];
      const Particle& sigma = chi.decayProducts()[ix].at(sign * 3212)[0];
      _h_psi[0]->fill((pbar.momentum() + sigma.momentum()).mass());
      _h_psi[1]->fill((Kp.momentum() + sigma.momentum()).mass());
    }
    else {
      if (chi.modeMatches(ix, 3, mode2)) {
        sign = 1;
      }
      else if (chi.modeMatches(ix, 3, mode2CC)) {
        sign = -1;
      }
      else
        continue;
      unsigned int iloc = chi.decaying()[ix].pid() == 10441 ? 0 : chi.decaying()[ix].pid() == 445 ? 2 : 1;
      const Particle& pbar = chi.decayProducts()[ix].at(-sign * 2212)[0];
      const Particle& Kp = chi.decayProducts()[ix].at(sign * 321)[0];
      const Particle& lam = chi.decayProducts()[ix].at(sign * 3122)[0];
      _h_chi[iloc][0]->fill((pbar.momentum() + Kp.momentum()).mass());
      _h_chi[iloc][1]->fill((Kp.momentum() + lam.momentum()).mass());
      if (iloc == 0) _h_pLam->fill((pbar.momentum() + lam.momentum()).mass());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) {
    normalize(_h_psi[ix], 1., false);
    for (unsigned int iy = 0; iy < 3; ++iy) normalize(_h_chi[iy][ix], 1., false);
  }
  normalize(_h_pLam, 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_psi[2], _h_chi[3][2], _h_pLam;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2013_I1203840);

} ```